Well, after looking at a bunch of threads for inspiration I have begun the process of building my own kit, mostly based on JerryW's. So far I've made a frame bag, and front/rear top tube bags. Lots of learning in the process but I'm getting better, ended up doing the rear top tube bag yesterday in a couple hours start to finish. The frame bag ended up being a lot smaller than expected just by looking at the frame, not much room in the triangle of the bike.
I also tried making the frame bag tapered in the front to add space, but it just kind of compresses when I try to attach it to the bike anyway, and even if it did the space added would probably be pretty minimal, so I wouldn't bother in my next one.
In any case, I'll keep updating this thread with progress.
The one question I had is how do you guys sew your bags with supports in the side (for the top tube bags, for example). I tried at first to sew in the supports, but realized quickly I couldn't turn the bag inside out if I had them in. What I ended up doing was having "pockets" on the top/bottom of the panels that would hold the plastic in place, but this leaves plastic exposed on the inside of the bag. I'm thinking there must be a more elegant solution but I can't think of how to do it in my head...
